The present invention relates, in general, to a patch antenna; and in particular, to a patch antenna generating both linearly and circularly polarized waves at the same time.
As wireless communication techniques have advanced, information communication terminals, such as mobile phones, PDAs, GPS receivers, etc., have been made available to many. These information communication terminals typically use a small, light patch antenna of a thin planar design. In general, the size of the patch antenna is in proportion to the wavelength of an intended frequency (e.g., the length of one side of the patch antenna is 0.5λ). Preferably, dielectric substrates having a high specific dielectric constant are used to make patch antennas smaller, provided the same frequency is used. However, the use of dielectrics having a high specific dielectric constant may degrade radiation performance of the antenna as the frequency band becomes narrow. Further, the use of dielectrics with a high dielectric constant may also increase the height of a patch structure constituting the antenna proportionally to the reduction ratio of dielectrics, which may impair the frequency band and gain of an antenna being used, and also may set height restrictions on the antenna. Furthermore, when the specific dielectric constant of dielectrics increases, the height of an antenna also increases proportionally to the reduction ratio thereof. This may lead to an increase in manufacturing costs and a drop in production yield. Overall, using dielectrics with a high specific dielectric constant places limitations on the size of an antenna.
As a result, patch antennas of various structures have been proposed.
The conventional patch antenna has a patch surface where a circularly polarized wave occurs in the right or left direction (RHCP or LHCP) by changing feeding position or patch structure.
Generally, when it comes to transmission/receiving operations between patch antennas, patch antennas having the same rotation direction (RHCP, LHCP) are preferably used to minimize the occurrence of a propagation loss between transmission/receiving antennas. However, when a circularly polarized antenna and a linearly polarized antenna are used for transmission/receiving operations, one would face, on one hand, a propagation loss of −3 dB, and on the other hand, the necessity of improving the transmission power and the receiving sensitivity in order to compensate for the loss of two polarized waves.
Accordingly, there remains a need in the art for patch antennas that do not generate any propagation loss.
The above information disclosed in the Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.